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over millions and millions of years. Can you recall the five main causes of evolution from memory?If you can't, hit rewind and watch that part again. But if you can, give yourself or your neighbor a big five-fingered high five.

Even the thumb itself is an adaptation formed through the process of natural selection. The evolution that we have described is referred to as microevolution, because it refers to a small change.However, this form of evolution may eventually lead to macroevolution, or speciation. Every organism on the planet shares ancestry with a single common ancestor. All living organisms on the planet are connected back in time through the process of evolution. Take a look at your own hand. It's an engineering masterpiece that was created by the five processes I just described,

The genes for individuals that are not adapted for their environment will gradually be replaced by those that are better adapted. Red hair is an example of one of these adaptations.Red hair is an advantage in the northern climates,because the fair skin allowed ancestors to absorb more light and synthesize more vitamin D. Thumbs up!However, this was a disadvantage in the more southern climates, where increased UV radiation led to cancer and decreased fertility. Thumbs down!

In science, we refer to this movement as gene flow. All four of the processes represented by our fingers can cause evolution. Small population size, non-random mating, mutations and gene flow. However, none of them lead to adaptation. Natural selection is the only process that creates organisms better adapted to their local environment.I use the thumb to remember this process.Nature votes thumbs up for adaptations that will do well in their environment,and thumbs down to adaptations that will do poorly.

The next finger is the middle finger. The M in the middle finger should remind you of the M in the word "mutation." If a new gene is added through mutation, it can affect the frequency. Imagine a gene mutation creates a new color of hair. This would obviously change the frequency in the gene pool. The pointer finger should remind you of movement. If new individuals flow into an area, or immigrate, the frequency will change. If individuals flow out of an area, or emigrate, then the frequency will change.

For example, if only four individuals survive an epidemic, then their genes will represent the new gene pool. The next finger is the ring finger. This finger should remind you of mating, because a ring represents a couple. If individuals choose a mate based on their appearance or location, the frequency may change. If redheaded individuals only mate with redheaded individuals, they could eventually form a new population. If no one ever mates with redheaded individuals, these genes could decrease.

If this frequency ever varies,then evolution has occurred. Evolution is simply change in the gene pool over time. Think about it in terms of the cards. If the frequency of the cards in the deck ever changes, evolution has occurred. There are five processes that can cause the frequency to change. To remember these processes,we will use the fingers on your hands,starting from the little finger and moving to the thumb. The little finger should remind you that the population can shrink. If the population shrinks, then chance can take over.

These genes are the gene pool.The 20 different genes are like cards in a deck that keep getting reshuffled with each new generation. Sex is simply a reshuffling of the genetic deck. The cards are reshuffled and passed to the next generation; the deck remains the same, 50 percent red. The genes are reshuffled and passed to the next generation; the gene pool remains the same, 50 percent red. Even though the population may grow in size over time, he frequency should stay at about 50 percent.

Imagine that a boat capsizes,and 10 survivors swim to shore on a deserted island. They are never rescued,and they form a new population that exists for thousands of years.Strangely enough,five of the survivors have red hair.Red hair is created when a person inherits two copies of the red gene from their parents. If you only have one copy of the gene,you won't have red hair.To make this easier, we will assume that the five non-redheads are not carriers of the gene. The initial frequency of the red-hair gene is therefore 50 percent, or 10 of 20 total genes.

The Five Fingers of Evolution.A thorough understanding of biology requires a thorough understanding of the process of evolution.Most people are familiar with the process of natural selection.However, this is just one of five processes that can result in evolution. Before we discuss all five of these processes,we should define evolution.Evolution is simply change in the gene pool over time.But what is a gene pool?And for that matter, what is a gene?Before spending any more time on genetics,let us begin with a story.

So what does this mean for humans? Are we also born with innate information written into our genomes that helps shape our neural circuits,and ultimately results in something we know?Could there be some knowledge that is unique and intrinsic to humans as a species?

So the theory is that a bird’s genes guide development of brain circuits that relate to singing and the ability to learn songs.Then, exposure to songs shapes those neural circuits to produce the songs that are typical to that species.Genetically encoded or innate behaviors aren’t unique to songbirds.They’re widespread in the animal kingdom. Spectacular examples include the long-distance migrations of monarch butterflies and salmon.

It doesn’t simply map single genes to single behaviors, but it exists.Genomes contain codes for proteins that guide brain development,such as molecules that guide the pathways of developing axons,shaping distinct circuits.Birds’ brains have so-called “song circuits”that are active when the birds sing.These circuits also respond to the song of a bird’s own species more strongly than to other species’ songs.

This means that basic information about the zebra finch song must be stored somewhere in its genome,imprinted there by millions of years of evolution.At first, this might seem odd,as we usually think of genetic code as a source of biochemical or physical traits,not something like a behavior or action.But the two aren’t fundamentally different;we can connect genomes to behavior through brain circuitry. The connection is noisy and quite complex.

at first.If isolated zebra finches start a new colony,the young birds pick up the isolate song from their parents.But the song changes from generation to generation.And after a few iterations,the melody actually starts to resemble the cultured songs sung by zebra finches in the wild.Something about the learning process must be hardwired, too,drawing the birds towards the same song patterns again and again.

But hide the same loudspeaker inside a toy painted to look like a zebra finch,and his learning improves.What if the baby never hears another zebra finch’s song?Interestingly enough, it’ll sing anyway.Isolated finches still produce what are called innate or isolate songs.A specific tune might be taught,but the instinct to sing seems to be hardwired into a songbird’s brain.Innate songs sound different from the “cultured” songs learned from other finches

First comes a sensory learning phase,when the baby finch hears the songs sung around it and commits them to memory.The bird starts to vocalize during the motor learning phase,practicing until it can match the song it memorized.As the bird learns, hearing the tutor’s song over and over again is helpful—up to a point.If he hears it too many times, thei mitation degrades—and the source matters. If the song is played through a loudspeaker,he can’t pick it up as easily.

Experienced listeners can even distinguish individual birds by their unique songs.So how do birds learn these songs in the first place?How do they know to mimic the songs of their own species?Are they born knowing how to sing?A lot of what scientists know about bird song comes from studying zebra finches.A baby male zebra finch typically learns to sing from its father or other males,starting while it’s still a fledgling in the nest.

These are just a few of the 4,000 species of songbirds.Most birds produce short, simple calls,but songbirds also have a repertoire of complex vocal patterns that help them attract mates,defend territory,and strengthen their social bonds.Each songbird species has its own distinct song patterns,some with characteristic regional dialects.

This is a song sung by a brown thrasher.But that’s just one of the thousand or more that it knows,and it’s not the only avian virtuoso.A wood thrush can sing two pitches at once.A mockingbird can match the sounds around it, including car alarms.And the Australian superb lyrebird has an incredible, elaborate song and dance ritual.